The present invention relates generally to solid-state lasers and, more particularly, to an intracavity frequency-doubled solid-state laser utilizing a neodymium-doped gadolinium vanadate (Nd:GdVO.sub.4) lasing material to generate a visible laser beam suitable for use in numerous applications, including surveying, measurement and equipment control in the construction and agricultural industries.
A low powered solid-state laser which employs a laser gain chip of stoichiometric lasing material, such as a neodymium pentaphosphate (NPP), in a single laser cavity is disclosed in commonly assigned U.S. Pat. No. 4,884,281 issued to Hawthorn et al. The laser gain chip is bonded to a frequency doubler chip by coupling material having a refractive index matched to the two chips to reduce reflections at the bonded chip surfaces. In response to pump light from a laser diode, the laser gain chip emits fundamental laser light which has its wavelength halved as it passes through the frequency doubler chip. The second harmonic light is then reflected within the laser cavity to generate an output laser beam in a conventional manner.
The efficiency and performance of an intracavity frequency-doubled solid-state laser are dependent upon a number of factors. For instance, the transparency of the lasing material to second harmonic light greatly affects the performance of the laser. Typically, lasing materials employed in prior intracavity, frequency-doubled solid-state lasers have had poor transparency to second harmonic laser light. Due to this poor transparency, prior laser designs have either isolated the laser gain chip from the second harmonic light or discarded the second harmonic light which does pass through the laser gain chip. Each of these designs has disadvantages which limit the performance and efficiency of the laser. The first design necessary prohibits creating a resonant condition in the laser and, therefore, the well-known advantages from creating a resonant condition are not obtainable. The second design creates a relatively inefficient laser since a portion of the second harmonic light is discarded. Consequently, the lasing material should have a high transparency to second harmonic light to reduce attenuation of the second harmonic light as it passes through the material.
As is well known, a lasing material should have a broad absorption band to reduce problems associated with frequency drift of the pump laser diode and should have a narrow fluorescent emission band to allow high peak gain. The lasing material should also have a high absorption rate for the pump energy emitted by the pump laser diode. A high absorption rate increases the efficiency of the laser and permits the use of thin crystals of lasing material.
Accordingly, there is a need for an improved low cost, intracavity frequency-doubled solid-state laser which employs a lasing material having a high transparency to second harmonic light, a high absorption rate of pump energy, a large absorption band and a narrow fluorescent emission band.